What is glycosylated haemoglobin (HbA1c)?
Haemoglobin is a protein in red blood cells that carries oxygen. It also forms a structure called glycosylated haemoglobin (HbA1C) when sugar (glucose) attaches to it. As the half life of a red blood cell is 90-120 days, measuring HbA1c levels in an individual’s blood reflects the average amount of glucose that has been attached to haemoglobin over the preceding 2-3 months. This is a more accurate determinate of the amount of glucose that is present within the body compared to a one off glucose test.
The HbA1c test is commonly used in the diagnosis and management of diabetes. It can also determine whether someone is pre-diabetic - where levels of sugars are not to a level where medications would be considered and lifestyle changes can prevent the development of diabetes.
Why is this analysis important?
In the diagnosis of diabetes and pre-diabetes
In the management of diabetes
Elevated levels are associated with an increased risk of Cardiovascular disease, Hypertension, Kidney failure and Obesity
Normal HbA1c values vary depending on the laboratory. The doctor will always evaluate the results based on several factors.
The following are results that you may receive:
Normal: HbA1C < 5.7%
Prediabetes: HbA1C 5.7% - 6.5%
Diabetes: HbA1C > 6.5%
Poorly controlled diabetes: HbA1C > 7%
When you receive your results you will receive two values - for example 5.4mmol/L (5.4%) . The initial figure is a measurement of the amount of glucose that is attached to the haemoglobin. The percentage which follows, relates to the haemoglobin protein HBA1, and what proportion of this protein has glucose bound to it.
If you have diabetes, normally you would have your blood test repeated every 3 to 6 months depending what your diabetic control is like.
The risk of diabetes increases with age.
HbA1C is not a substitute for daily monitoring of glucose levels in those who are on insulin treatment.
Tests that include this marker
Estimation of blood glucose control in diabetes mellitus. David K McCulloch, MD. UpToDate Aug 08, 2018 Sherwani SI, Khan HA, Ekhzaimy A, Masood A, Sakharkar MK.
Significance of HbA1c Test in Diagnosis and Prognosis of Diabetic Patients. Biomark Insights. 2016;11:95‐104. Published 2016 Jul 3. doi:10.4137/BMI.S38440